What Causes the Center to Collapse After Blooming in Pour-Over Coffee | A Brief Analysis of the Depression Pit Formation in Pour-Over Coffee

The Coffee Bloom Dilemma: Understanding Pour-Over Coffee Collapses

In pour-over coffee brewing, the bloom stage represents our "first encounter" with the coffee grounds. If a complete, uniform "hamburger" shape appears in the coffee bed, this establishes the foundation for "victory." If the coffee bed shows no expansion at all, it's likely that the coffee beans are not fresh, and the resulting coffee won't taste good.

However, there's a particular scenario where the coffee bed expands during the bloom watering, but soon after, the center collapses and sinks inward. Is this situation normal?

Understanding the Phenomenon

First, FrontStreet Coffee will analyze why this phenomenon occurs. If the coffee bed shows expansion, this indicates that the coffee grounds are releasing gas, which rules out the possibility of stale coffee beans. The collapse after expansion mainly occurs because when the coffee bed releases gas, the gaps between coffee particles become larger. After the gas is released, this structure becomes loose. If the pressure on the center top is too great, it cannot maintain such a fluffy structure, so the middle collapses.

Causes of Coffee Bed Collapse

Excessive Water Amount

Generally, bloom watering should be approximately twice the amount of coffee grounds. However, sometimes we accidentally add too much water. For example, when FrontStreet Coffee uses a light roast coffee bean for demonstration, with 15g of coffee grounds and 30ml of water poured in small circles during blooming, the coffee bed remains puffed up at 30 seconds. However, when 40ml of water is poured in small circles at the center with 15g of coffee grounds, we can observe that the water level of the coffee bed rises, and at 23 seconds, as the bloom liquid flows downward, the center of the "hamburger" coffee bed also shows slight collapse.

Too "Aggressive" Watering

Generally, bloom watering involves pouring water from the center outward in circles, and the coffee "hamburger" also expands slowly from the center to the surroundings. With some fluffy coffee grounds (such as medium-dark roast), even pouring in small circles at the center can make the coffee "hamburger" expand from the center to the surroundings.

Therefore, in terms of results, pouring in small circles or large circles actually doesn't make much difference. Everyone can use their judgment based on the actual situation. However, gentle versus aggressive watering methods have different effects on the state of the coffee bed.

Gentle watering doesn't significantly impact the structure of the coffee bed; whereas more aggressive watering, if focused only on small circles at the center, will create larger gaps between the coffee bed particles directly impacted by the water stream. The center's support mainly comes from gas release obstructing the water's downward flow. When the gas is completely released, the water flows downward, leaving behind a hollow coffee bed that naturally collapses.

Coffee Grounds Too Coarse

If the coffee grounds are ground too coarsely, water will flow into the lower pot before it has time to penetrate the interior of the coffee particles. When coffee grounds first contact water, the surface releases gas, causing the gaps between coffee particles to expand (i.e., bloom). However, if water flows into the lower pot before entering the interior of the coffee particles, these gaps lack support and collapse easily occurs.

Conclusion

A collapse during blooming is clearly not a normal phenomenon; it reflects problems with our parameters or techniques. Therefore, when we encounter bloom collapse during brewing, we need to "prescribe the right medicine" by identifying and solving problems from the aspects of parameters and techniques.

Important Notice :

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